Creating a usb charger for a 3.7v 1500mah battery

Discussion in 'General Electronics Chat' started by Ben Barker, Dec 10, 2014.

  1. Ben Barker

    Thread Starter New Member

    Dec 10, 2014
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    Im looking to find out how i can charge a 3.7v 1500mah battery via a usb port.
    i understand usb provides 5v 500ma so in a perfect world would give 3 hours charge time. Obviously some numbers need to be controlled but i can neither find anything in existence or any information on how to do this.
    Any help would be appreciated ! thank you in advance!
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    My first question, have you looked for a commercially available option? Before we help guide you to a design, What features of a commercially available, off-the-shelf solution is not meeting your needs?
     
  3. Ben Barker

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    Dec 10, 2014
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    Ive had a reasonably decent look but cant find anything that addresses charging a battery such as this.
    Im wanting to create a product which is powered by one of these babys and can be charged at your desk...
     
  4. GopherT

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  5. Papabravo

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    Feb 24, 2006
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    This is a misconception. The default current available is 100 mA. To get more you are supposed to negotiate, using the USB protocol, with the hub or master device. That device may or may not grant the request. Debugging a USB protocol device is not to be undertaken lightly and certainly not without some debugging tools.
     
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  6. Ben Barker

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    Dec 10, 2014
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    Correct but not what im looking for. This needs to be reasonably small as it will be charging a battery for a product of similar size (dont want the whole package to be too bulky)
    Although this looks perfect i discarded it as i saw on another page these "adifuit" chargers should only be used to charge adifruit batteries ?
    Do you have any insight on this ? its size is perfect but i cant be buying at that price to fit into a product so id need to find a manufacturer.
    Kind regards Ben.
     
  7. Ben Barker

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    Dec 10, 2014
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  8. takao21203

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  9. Alec_t

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    Sep 17, 2013
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    Are you aware that charging lithium batteries safely is not a trivial task? Get it wrong and you could be calling out the emergency services :eek:.
     
  10. Ben Barker

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    Dec 10, 2014
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    Exactly why im not attempting to bundle something together myself haha. As the product it will be a part of will be sold i need to find a manufacturer who can provide a legit and safe charger.
     
  11. takao21203

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    pretty much trivial items. These IC are just shunts, and they turn off at some voltage. i sold 100s of these small modules already. They work for all small lithium batteries.
     
  12. Papabravo

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    I see a trip to China in your future.
     
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  13. Ben Barker

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    Dec 10, 2014
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    Already looking there! ha
     
  14. ian field

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    Oct 27, 2012
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    For quite some time now, I've been getting away with a TL431 shunt regulator. Its for my e-cigarette and is in daily use with 2 batteries on charge while I use a third.

    About 8.2 Ohms is about right to limit current, the shunt voltage must be calibrated precisely for safe charging.

    On my charger, I anticipated the worst possible case of the TL431 failing short circuit; I've included a low forward drop Shottky barrier diode in series with the battery - you do of course have to measure the diode Vf under charging conditions and add this to the voltage calibration.

    There have been no problems with mine so far, once or twice I've forgotten to change over batteries in the morning, so the batteries have been left continuously charging for as much as 48h. If you anticipate that the charger could be left unattended for more than 24h, I would highly recommend one of those plug in mains timers between the charger and the wall socket.
     
  15. takao21203

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    what stops you from using a TP4056 etc.?? Its the easiest way to charge LI batteries.
     
  16. JWHassler

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  17. Ben Barker

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    Dec 10, 2014
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    So your using your ecig charger ? slightly modified?

    So i could use a module similar to the one i linked early but i would need to add what you have linked in order to protect the battery?
    Have to apologies, my only electrical knowledge is that of A Level Physics! haha.
    So thank you all for helping !
     
  18. ian field

    Distinguished Member

    Oct 27, 2012
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    Before I got into making my own chargers - I acquired a Nikon camera with a lithium battery but minus its charger - I stripped a Vapourlites E-cigarette for the little capsule containing the end of charge cut off circuitry and charged the Nikon battery with the Vapourlites USB adaptor - it took a few days to charge the much bigger battery than it was intended for, but got there in the end.
     
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